Temporal And Spatial Variation Characteristics Of Drought In The Yihe River Basin And Its Quantitative Attributio

Under the dual impact of global climate change and human activities,in recent years,the frequency and intensity of drought in China have gradually increased,bringing serious impacts on economic and social development and ecological environment protection.At the same time,there are significant spatiotemporal differences in drought changes and their driving mechanisms in different regions.Therefore,based on distributed hydrological models and geographic information technology,studying the spatiotemporal characteristics of drought on a watershed scale and quantitatively assessing the impact of climate change,land use change,and other human activities on drought can not only improve the understanding of the evolution mechanism of the water cycle,but also have important scientific significance for improving the level of disaster prevention and mitigation,and responding to climate change.This study takes the Yihe River basin,an important tributary of the Huaihe River basin and the larger river in the Yishusi River system,as an example.Based on the SWAT(Soil and Water Assessment Tool)hydrological model and the PDSI(Palmer Drought Severity Index)drought index,a SWAT-PDSI model was constructed to reflect the impact of underlying surfaces on the drought process.This model revealing the spatiotemporal characteristics of drought in the basin.Temperature,precipitation,the impact of land use/cover change(LUCC)and other human activities on drought change was quantitatively evaluated through controlled experiments.At the same time,representative extreme drought events in the study area were extracted based on the daily scale SPEI(Standardized Precision Evapotranspiration Index)index,and the formation and evolution characteristics of typical extreme drought events and their influencing factors were analyzed.The research results are of great significance for formulating watershed water resource management strategies.The main research results are as follows:(1)From 1980 to 2019,the SWAT-PDSI drought index showed a slightly decreasing tr end,with a change rate of-0.02/10a,the precipitation in the Yi River basin showed a down ward trend(-2.7mm/10a),while the temperature showed a significant upward trend(0.13℃/10 a,p<0.05),indicating that the drought degree in the Yi River basin has intensified,espec ially in the central region of the basin.(2)The land use change in the Yihe River Basin is mainly characterized by a decrease in the area of dry land(149 km~2)and an increase in the area of construction land(135 km~2),with changes of-1.77%and 18.96%,respectively.(3)Climate fluctuation is the main driving factor of drought change,with a contributio n rate of between 68%and 84%,and its contribution to drought is gradually increasing.Am ong them,the contribution rate of temperature exceeded that of precipitation in 2010-2019,which means that temperature has become the most important climatic factor affecting drou ght.The contribution rates of LUCC to drought change in 1990-1999,2000-2009,and 2010-2019 were 7.8%,18%,and 12.6%,respectively.This indicates that the relative contribution of other human activities to drought change is gradually weakening.(4)According to the formation process and evolution characteristics of drought events,typical extreme drought events(moderate drought lasting for 3 days or more)in the study a rea can be divided into two types:single peak type(accounting for 1/3)and multi peak type(accounting for 2/3).The former mainly occurs in autumn,while the latter both occur in su mmer,and most of them are sudden onset droughts.